The overall aim is to define the mechanisms of immune injury to the lungs in occupationally related pulmonary diseases. Using an experimental model in rabbits which is monitored by changes in areterial blood gases, attempts are being made to produce the disease hypersensitivity pneumontits. Animals are immunized via the aerosol route with classical protein antigens or fungal spores known to produce spontaneous human disease. These animals are then challenged and following data obtained at timed intervals thereafter: arterial Pa 2, CH50 titer, and quantitative precipitin production. Further studies also include the study of cell mediated reactivity of these animals to the antigen in question. In this manner, the validity of claims on mechanism of pathogenesis of this disease can be examined, e.g., Type II, III, IV, Mixed, or complement activation. Also being studied are the effects of the physical and chemical nature of the inhalant on the (1) typed of immunologic effector cells produced in the lung and (2) on the type of inflammatory mediators participatin in occupational respiratory diseases. BIBLIOGRAPHIC REFERENCES: Burrell, R.: Immunological Reflections on Asbestosis. Environ. Health Perspect. 9:297-298, 1974. Burrell, R.: Further Studies on the Effect of Lung Antibodies on the Pathogenesis of Tuberculosis. J. Lab. Clin. Med. 86:741-745, 1975.